1. Field of the Invention
This invention generally relates to a dust collector for collecting air-born dust in the form of liquid droplets and solid particles, and, in particular, to an electrostatic precipitator for use in collecting dust and mist in various coal-fired boilers, cement plants, iron manufacturing plants, metal refining plants, chemical plants and incinerators.
2. Description of the Prior Art
An electrostatic precipitator is well known in the art for removing dust and other particles from a gas by charging the particles and having them collected on collector plates. Typically, such an electrostatic precipitator includes a pair of parallel plates and a corona wire located at the center between the parallel plates, in which a high voltage is applied to the corona wire with the parallel plates being grounded, and a gas containing dust is passed through the pair of parallel plates whereby the dust becomes charged and collected onto both of the parallel plates. Another typical form of electrostatic precipitator includes a cylindrical tube and a corona wire extending along the longitudinal center of the tube, in which a high voltage is applied to the corona wire with the tube being grounded, and a gas containing dust is passed through the tube whereby the dust becomes charged and collected onto the tube. Such an electrostatic precipitator is quite efficient in collection of dust and mist, but since the collection site is generally flat with respect to the flow direction of gas, the collected dust tends to be reentrained into the gas flow, thereby decreasing the collection efficiency. Interestingly, larger particles are easier to collect, but larger particles are also easier to reentrain. It should also be noted that the chances of occurrence of such reentrainment are higher if the gas flow velocity is higher.
It is also known to utilize the inertia effect to remove droplets and particles from a gas, in which case a deflector plate is typically provided to change the course of gas flow thereby causing particles having mass to deviate from the streamline of gas flow to hit the deflector plate to be collected thereon. Such a dust collector is typically shown in Japanese Patent Post-Examination Pub. No. 49-36186. It is to be noted, however, that such a dust collector relying on the inertia effect of each particle is efficient in collecting relatively larger-sized particles, e.g., 10 microns or more in diameter, but its collection efficiency significantly drops for smaller-sized particles.
In view of the recent trend for making regulations against air pollution more stringent, it is desired to provide an improved device for collecting dust and mist at high efficiency.